Seventy-eight plasma samples obtained from 54 patients with familial Mediterranean fever were examined for the presence of cryofibrinogen. Cryofibrinogen was found in all 18 samples obtained from 15 patients while experiencing 16 attacks. None was found in the 60 samples obtained in the intervals between attacks.
Shamir H, Pras M, Sohar E, Gafni J. Cryofibrinogen in Familial Mediterranean Fever. Arch Intern Med. 1974;134(1):125-126. doi:10.1001/archinte.1974.00320190127019